RIO DE JANEIRO, BRAZIL – Future Covid-19 vaccines will not protect everyone who gets them. To have 100 percent efficacy is always a dream, but it is quite possible that some of the first vaccines against the novel coronavirus will be so distant from this 100 percent that it would be better to have nothing, a group of experts from the World Health Organization (W.H.O.) now cautions.
None of the 33 experimental vaccines currently being tested in humans has yet proven its safety and efficacy. “There is a risk that political and economic pressures to swiftly introduce a vaccine against Covid-19 could lead to the widespread introduction of one that is actually very ineffective, that would only reduce the incidence of Covid-19 by ten to twenty percent,” according to Colombian doctor Ana María Henao, coordinator of the W.H.O. Diagnostic and Vaccine Research and Development Plan.
Donald Trump’s government promised to start administering the vaccine in the US as early as October, well in time for the final stage of the campaign for the November 3rd presidential election.
It is unclear what the minimum efficacy required to halt the pandemic would be. The W.H.O. prefers a single dose vaccine with over 70 percent efficacy, but would conform to a two-dose vaccine with 50 percent efficacy, according to the parameters agreed in April. A recent simulation, headed by researcher Bruce Y. Lee of New York City University, suggests that to prevent new epidemics with no other control measures, the vaccine would have to offer 60 percent efficacy if administered worldwide, over 70 percent if only three-quarters of people are vaccinated, and 80 percent if only 60 percent of the population is covered.
“We still don’t know how effective [the current experimental vaccines] will be,” conceded Anthony Fauci, director of the US National Institute of Allergies and Infectious Diseases. In any case, even a utopian vaccine with 100 percent efficacy would not be very useful if half of citizens were to decide not to use it, according to Lee’s simulation.
“The use of an ineffective vaccine could worsen the Covid-19 pandemic if authorities wrongly assume it substantially reduces risk, or if vaccinated people mistakenly believe they are immune, reducing other Covid-19 control measures or compliance therewith,” W.H.O. experts caution in an article published in The Lancet medical journal.
The researchers also warn of a phenomenon known as biocreep. The efficacy and safety of current experimental vaccines are analyzed by comparing the results of tens of thousands of vaccinated volunteers with a control group of unvaccinated individuals. If there are many fewer Covid-19 patients among those vaccinated and nothing abnormal is recorded, the vaccine will be effective and safe.
But if, given the emergency, an ineffective vaccine is allowed and it becomes the standard preventive treatment, the subsequent experimental vaccines would not have to prove to be better than a placebo, but rather that they are no worse than the already approved one. Biocreep is a possible phenomenon in which so-called noninferiority trials, by only comparing the efficacy of new drugs with that of existing drugs, can allow inferior treatments to go to market.
To ensure the efficacy of future vaccines, the W.H.O. team of experts proposes to study multiple experimental vaccines simultaneously, comparing them with each other and with a placebo. Researchers believe that a trial of between three and six months would be sufficient to identify a vaccine capable of halving the risk. W.H.O. calls on vaccine developers to join this future multiple analysis, called Solidarity. Some of them – such as Oxford University, US Moderna, Inovio, Arcturus Therapeutics and Johnson & Johnson, German biotech company Curevac and Chinese CanSino Biologics- signed a declaration in April in which they committed to cooperate and share data. They have all started to test their different experimental vaccines in humans, although separately for now.
“If we start to inoculate people, we will need to know that no vaccine is 100 percent effective. Some people will get sick despite my vaccine,” acknowledged a few days ago Israeli doctor Tal Zaks, scientific director of the Moderna Laboratory, a US biotechnology company that is testing an experimental vaccine on 30,000 volunteers in the US. Zaks said his greatest concern is that the epidemic is temporarily controlled and, in the absence of contagion, it is impossible to determine whether or not the vaccine works. The W.H.O. International Solidarity trial would prevent this risk of failure by offering “hundreds” of places to test the vaccines.
“A worldwide trial of multiple vaccines with a shared control group could provide more reliable and faster results […], expediting the discovery of several safe and effective vaccines,” the researchers note. Among the signatories are Philip Krause, vaccine expert from the US drug agency (the FDA), and epidemiologist Richard Peto, from Oxford University, both in the expert group for the Solidarity trial. “The cost of the trial will be a fraction of the social cost of Covid-19, and this global cooperation could defeat nihilism and nationalism in vaccines,” they add.
Spanish Health Minister Salvador Illa said the first doses of the future Oxford vaccine will reach his country in December “if all goes well” in clinical trials currently underway. But the fact that they will come does not mean they will be administered. The European Medicines Agency estimates that “at least until the start of 2021” no vaccine will be eligible for authorization.
Wealthy countries have rushed to reserve experimental vaccines without waiting for clinical trials to be completed. The goal is to gain time in a pandemic that is currently killing 40,000 people a week worldwide. The EU holds draft agreements to buy 300 million Oxford vaccine doses, 300 million Sanofi-GSK laboratory products, 225 million Curevac doses, 200 million from Johnson & Johnson and 80 million from Moderna. There is still no guarantee that any of them will work.
Source: El País